1. Field of the Invention
The present invention generally relates to a thyristor ignition circuit. More specifically, the present invention is directed to a thyristor ignition circuit suitable for switching a switching element employed in, for instance, a television receiver in order to correct vertical deflection distortion.
2. Description of Prior Art
To correct pincushion distortion occurring in a television receiver, a parabolic current is produced by switching a switching element. Normally, when a thyristor is employed as this switching element, for example, the pincushion correction circuit is arranged as shown in FIG. 1. In this thyristor pincushion correction circuit, both of thyristors 61 and 62 are connected between one signal terminal 64 and the other signal terminal 65 in such a manner that an anode of one thyristor 61 is connected to a cathode of the other thyristor 62, and similarly an anode of the other thyristor 62 is connected to a cathode of the first thyristor 61 (so-called "cross-coupling connection"). When a predetermined pulse is inputted to a primary coil 63a of a transformer 63, pulses are outputted from secondary coils 63b and 63c thereof.
With this circuit arrangement, when a predetermined pulse is applied to the primary coil 63a of the transformer 63, the pulses are derived from the secondary coils 63b and 63c, respectively, and then these pulses are supplied to gates of the above-described thyristors 61 and 62. As a result, these thyristors 61 and 62 are turned ON. Accordingly, for example, a current of a positive direction flows from one signal terminal 64 through the anode-to-cathode path of one thyristor 61 to the other signal terminal 65, whereas another current flows from one terminal 65 via the anode-to-cathode path of the other thyristor 62 to the other signal terminal 64.
However, when these thyristors are ignited via the gate electrodes thereof by these ignition pulse, a horizontal line appears on a screen of a television receiver, as represented in FIG. 2, due to insensitivity of the thyristors (which will be discussed later).